The overall goals of this project are to 1) determine the primary effect of morphine-like drugs on the cholinergic system in the mammalian brain and 2) compare the effects of barbiturates to determine if they act differently from the narcotics on this transmitter system. These goals will be pursued using brain slices from drug-treated rats. In preliminary experiments the time of day at which morphine causes the greatest change in brain acetylcholine (ACh) will be determined and then the light-dark schedule of the animals will be adjusted so that this time is convenient for the investigators. The hypothesis to be tested is that morphine inhibits ACh release which causes an increase in tissue concentrations of ACh which in turn causes a decrease in ACh synthesis. The effects of the drugs will be tested on ACh synthesis (measuring total amounts in vivo and after incubation in vitro, the activity of choline acetylase, and the incorporation of radioactive precursors in vitro), ACh storage (measuring amounts of ACh in subcellular fractions in the tissue) and ACh release (measuring the amount released into the medium from incubating slices). Further experiments will examine in greater detail the mechanisms by which morphine inhibits ACh release if the hypothesis is verified.